System and method for tracking and archiving battery performance data

ABSTRACT

An intelligent rechargeable battery pack having a battery management system for monitoring and controlling the charging and discharging of the battery pack is described. The battery management system includes a memory for storing data related to the operation of the battery, and the battery management system is also configured to communicate the data related to the operation of the battery to other processors for analysis.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of priority to U.S. ProvisionalApplication No. 61/522,204, filed Aug. 10, 2011, and U.S. ProvisionalApplication No. 61/480,286, filed Apr. 28, 2011.

This application is related to U.S. application Ser. No. 13/459,004, nowU.S. Pat. No. 9,437,848, entitled “Latch Mechanism For BatteryRetention,” filed Apr. 27, 2012;

U.S. application Ser. No. 13/458,973, now U.S. Pat. No. 8,729,957,entitled “Battery Management System With MOSFET Boost System,” filedApr. 27, 2012;

U.S. application Ser. No. 13/458,988, entitled “System and Method ForAutomatic Detection Of Battery Insertion,” filed Apr. 27, 2012;

U.S. application Ser. No. 13/458,952, now U.S. Pat. No. 9,099,877,entitled “Battery Management System For Control of Lithium Power Cells,”filed Apr. 27, 2012; and

U.S. application Ser. No. 13/459,007, now U.S. Pat. No. 9,337,668,entitled “Viral Distribution of Data, Operating Parameters and SoftwareUsing A Battery As A Carrier,” filed Apr. 27, 2012; the entireties ofwhich are hereby incorporated herein by reference.

FIELD OF THE INVENTION

The invention is directed to a battery pack for providing power to adevice. More specifically, the invention is directed to a battery packand battery management system for managing the charging and dischargingof the battery pack, and also having a capability of receiving,transporting, and downloading data, information and software programs todevices suitably configured to accept such.

BACKGROUND OF THE INVENTION

Cardiopulmonary resuscitation (CPR) is a well-known and valuable methodof first aid used to resuscitate people who have suffered from cardiacarrest. CPR requires repetitive chest compressions to squeeze the heartand the thoracic cavity to pump blood through the body. Artificialrespiration, such as mouth-to-mouth breathing or a bag mask apparatus,is used to supply air to the lungs. When a first aid provider performsmanual chest compression effectively, blood flow in the body is about25% to 30% of normal blood flow. However, even experienced paramedicscannot maintain adequate chest compressions for more than a few minutes.Hightower, et al., Decay In Quality Of Chest Compressions Over Time, 26Ann. Emerg. Med. 300 (September 1995). Thus, CPR is not often successfulat sustaining or reviving the patient. Nevertheless, if chestcompressions could be adequately maintained, then cardiac arrest victimscould be sustained for extended periods of time. Occasional reports ofextended CPR efforts (45 to 90 minutes) have been reported, with thevictims eventually being saved by coronary bypass surgery. See Tovar, etal., Successful Myocardial Revascularization and Neurologic Recovery, 22Texas Heart J. 271 (1995).

In efforts to provide better blood flow and increase the effectivenessof bystander resuscitation efforts, various mechanical devices have beenproposed for performing CPR. In one variation of such devices, a belt isplaced around the patient's chest and an automatic chest compressiondevice tightens the belt to effect chest compressions. Our own patents,Mollenauer et al., Resuscitation device having a motor driven belt toconstrict/compress the chest, U.S. Pat. No. 6,142,962 (Nov. 7, 2000);Bystrom et al., Resuscitation and alert system, U.S. Pat. No. 6,090,056(Jul. 18, 2000); Sherman et al., Modular CPR assist device, U.S. Pat.No. 6,066,106 (May 23, 2000); and Sherman et al., Modular CPR assistdevice, U.S. Pat. No. 6,398,745 (Jun. 4, 2002); and our application Ser.No. 09/866,377 filed on May 25, 2001, our application Ser. No.10/192,771, filed Jul. 10, 2002 and our application Ser. No. 12/726,262,filed Mar. 17, 2010 show chest compression devices that compress apatient's chest with a belt. Each of these patents or applications ishereby incorporated by reference in their entireties.

Since seconds count during an emergency, any CPR device should be easyto use and facilitate rapid deployment of the device on the patient. Ourown devices are easy to deploy quickly and may significantly increasethe patient's chances of survival.

One important aspect of such devices is the need for small, powerful yetreliable power supply to power the device. It is not uncommon for CPR tobe administered for at least thirty minutes. Thus, the power supply mustbe capable of delivering sufficient energy to the motor driving thecompression device for at least that length of time. Moreover, the powersupply must be relatively light weight, so as to enhance portability ofthe chest compression device, yet it must deliver its power for anextended period of time without significant voltage or current drop offto ensure consistency of compression throughout the treatment period.

Current batteries typically have no way to store data or informationrelated to the overall history of use or performance of the battery.Such data would be useful because it would allow for analysis of theperformance of the battery and potentially provide trend informationregarding charging and discharging cycles, location of the battery, andthe frequency of various problems or faults experienced by the battery.

When such batteries are used in conjunction with devices like mechanicalCPR devices that are typically used by first responders such as the firedepartment or emergency medical technicians, the batteries tend to beexchanged between users. In such a case, a battery assigned to one firestation or ambulance crew may be picked up inadvertently by the crewfrom another station or ambulance during an emergency. In general,previous batteries have lacked an ability to sense their location andthus it was not possible to track the location of the battery in theevent that the battery needed to be upgraded or recalled for maintenanceor replacement.

As can be imagined, it is not atypical for batteries to be roughlyhandled during such emergency situations. Until now, however, thebatteries have lacked the ability to sense a parameter associated withrough handling and thus could not make a record of it for futureanalysis to determine the extent to which rough handling affects thelife and performance of the battery.

Even if a battery were capable of sensing and recording the type ofevents described above, batteries were typically unable to easilycommunicate the data stored in their memories to computer, server orother processor for analysis. At best, a battery memory, if existent atall, could be queried only when the battery was returned for maintenanceor replacement.

What has been needed, and heretofore unavailable, is a light weight,reliable intelligent battery pack having a memory for storing a recordof various events that would be useful in analyzing the performance,location and life of the battery. Such a memory would be able to bequeried by external systems, such as servers, or other computers andprocessors either directly from a communication system included in thebattery, or through a local or wide area network, intranet or theInternet. Such an accessible memory would allow the location of thebattery to be tracked, which would be advantageous in cases where thebattery needed to be updated or replaced. The present inventionsatisfies these, and other needs.

SUMMARY OF THE INVENTION

In a most general aspect, the invention provides a high-performancebattery pack capable of reliably providing high power and current topower a device for a prolonged period of time. Moreover, the batterypack includes a battery management system that monitors and controls allaspects of battery operation, including charging and discharging of thebattery. The battery management system is also capable of recordingevents that occur during the lifetime of the battery pack, andcommunicating those events for later analysis. The battery managementsystem is also capable of being updated with enhanced or improvedoperating parameters, and is capable of managing various batterychemistries to provide for forward and backwards compatibility.

In yet another further aspect, the battery management system of thepresent invention may include one or more processors for monitoring andcontrolling the various functions of the battery management system. Inanother aspect, the one or more processors may be configured tocommunicate with internal and/or external memory storage or devices toprovide for storage of events that occur during the lifetime of thebattery pack. In still another aspect, the processors may be configuredto communicate not only with internal or external storage media ordevices, but may also be configured to communicate over a network withother processors, storage media or devices, or even other batteries orbattery chargers. The network may be either wired or wireless.

In still another aspect, the battery management system of the presentinvention includes a memory in which can be stored data and informationrelated to the performance of the battery. In an alternative aspect, thebattery management system may also include a position locating system,such as, for example, a system based on global positioning satellite(GPS) technology, and the memory may be configured to store data andinformation related to the location of the battery.

In still another aspect, the battery may include a sensor, such as anaccelerometer for sensing how the battery is handled during use, storageand transport, and the memory is configured to store information relatedto the handling of the battery so that the information and data may beretrieved and analyzed.

In a further aspect, the present invention includes a battery that has amemory that is used as a carrier to provide for the viral, or rapid,distribution of data, operating parameters and/or software updates toother batteries or the equipment that is powered by the batteries. Inone aspect, the battery obtains updated data, operating parametersand/or software from the memory of a battery charger that is used torecharge a discharged battery. In another aspect, the recharged batterycarries the updated data, operating parameters and/or software to apiece of equipment that utilizes the battery for power, and, onceconnected to the equipment, provides for distribution of the updateddata, operating parameters and software to a memory and/or processor ofthe equipment. In still another aspect, the battery checks the memory ofthe charger or charging circuit, or the memory of the equipment ordischarging circuit, to determine the relative date of data, operatingparameters and/or software on both the battery and the equipment, andeither provides updated data, operating parameters and/or software tothe equipment, or retrieves later data, operating parameters and/orsoftware from the equipment to update the memory of the battery and/orfurther distribute the updated data, operating parameters and/orsoftware to other batteries or equipment.

In yet another aspect, the present invention includes a battery pack forpowering a device, comprising: a rechargeable battery having a positiveand a negative terminal; a sensor for monitoring a parameter related tooperation of the rechargeable battery, a memory for storing data relatedto operation of the rechargeable battery, and a processor in electricalcommunication with the sensor and the memory, the processor configuredto receive signals from the sensor and to store the data related tooperation of the rechargeable battery extracted from the signals fromthe sensor in the memory, the processor also configured to retrieve thestored data from the memory and to communicate the stored data to aprocessor external to the battery pack. In one alternative aspect, thememory is an event archive.

In an alternative aspect, the processor external to the battery is aprocessor located in a battery charger. In yet another aspect, theprocessor is also configured to communicate with a processor in a devicebeing powered by the battery pack, and wherein the processor in thedevice being powered by the battery pack communicates informationrelated to an operational parameter of the device being powered by thebattery pack to the processor for storage in the memory. In stillanother aspect, the data related to the operation of the rechargeablebattery includes history data related to the operation of therechargeable battery, and in yet another aspect, the data related to theoperation of the rechargeable battery includes run time data.

In still another aspect, the data related to the operation of therechargeable battery includes data selected from the group consisting ofnumber of times the battery has been charged or discharged, a maximum orminimum lifetime load test voltage, a maximum or minimum lifetime loadtest current, a maximum or minimum lifetime load test power, a maximumlifetime peak charge temperature, a temperature sensor ID, a minimumlifetime peak charge temperature, a maximum lifetime peak dischargetemperature, a lifetime full charge cycle count, a lifetime conditioncycle count, a lifetime low power count, a lifetime wakeup count, alifetime reset count, an lifetime total fault count, a lifetime cellunder-voltage fault count, a lifetime over-current fault count and alast condition cycle time.

In yet another aspect, the data includes data related to identificationof the rechargeable battery, and in an alternative aspect, the datarelated to identification of the rechargeable battery is a serialnumber. In yet another aspect, the data related to operation of therechargeable battery includes a time stamp to identify a data and timethe data was stored in the memory.

In still another aspect, the processor located in the charger isprogrammed to request that the processor of the rechargeable batterycommunicate the data stored in the memory to the processor located inthe charger, and wherein the processor located in the charger stores thereceived data in a memory associated with the processor located in thecharger. In yet another aspect, the processor located in the charger isconfigured to communicate the data stored in the memory associate withthe processor located in the charger to a server remote from thecharger.

In a further aspect, the battery pack further comprises: circuitry fordetermining a location of the battery pack from location signalsreceived by a receiver in the battery pack; and wherein the processorstores the location of the battery pack in the memory. In anotheraspect, the processor stores the location of a device powered by thebattery pack in the memory.

In still another aspect, the sensor is an accelerometer and theprocessor is configured to determine data related to forces experiencedby the battery pack and also configured to store the data related to theforces experienced by the battery pack in the memory. In another aspect,the processor is configured to retrieve the stored data from memory inresponse to a request for the data received from a processor external tothe battery pack. In still another aspect, the processor is configuredto retrieve the stored data from memory and communicate the stored datato a processor external to the battery pack in response to theoccurrence of an event sensed by the processor that causes the processorto execute a programmed command code.

In still another aspect, the present invention includes a battery packfor powering a device, comprising: a rechargeable battery having apositive and a negative terminal; a battery management system inelectrical communication with the rechargeable battery, including asensor for monitoring a performance parameter related to operation ofthe rechargeable battery, a memory for storing data related to operationof the rechargeable battery, and a processor in electrical communicationwith the sensor and the memory, the processor configured to receivesignals from the sensor and to store the data related to operation ofthe rechargeable battery extracted from the signals from the sensor inthe memory, the processor also configured to retrieve the stored datafrom the memory in response to a request for the data received from aprocessor external to the battery pack.

Other features and advantages of the invention will become apparent fromthe following detailed description, taken in conjunction with theaccompanying drawings, which illustrate, by way of example, the featuresof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a method of performing chest compressions on apatient by using a mechanical chest compression device.

FIG. 2 is perspective view of the mechanical chest compression device ofFIG. 1 showing the bottom and front sides of the device

FIG. 3 is a perspective view of the mechanical chest compression deviceof FIG. 1 showing the bottom and rear cover plates removed.

FIG. 4A is perspective view of a battery pack in accordance with thepresent invention showing a battery latch disposed on a front side ofthe battery pack.

FIG. 4B is a perspective view of the battery pack of FIG. 4A showing aconnector, indicator and button disposed on a back side of the batterypack.

FIG. 5 is an exploded perspective view illustrating various componentsof one embodiment of a battery pack of the present invention.

FIG. 6 is a schematic diagram of an embodiment of battery managementsystem in accordance with principles of the present invention.

FIG. 7 is a schematic diagram of an embodiment of a system forretrieving information stored in an event archive of the batter inaccordance with principles of the present invention.

FIG. 8 is a schematic representation of the viral transmission of data,information and/or software programs or commands using an embodiment ofthe battery of the present invention as a carrier.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The various embodiments of the present invention are directed toproviding a rechargeable battery for powering mobile equipment,particularly medical devices. The embodiments of the invention areparticularly advantageous when the battery is required to provide alarge amount of current over a predictable period of time. Moreover, theembodiments of the invention include a battery management system thatcontrols all aspects of the operation of the battery, and also includesa memory in which events related to the battery that occur during thebattery's lifetime are stored. Moreover, embodiments of the batterymanagement system include the capability of accommodating batteriesusing different battery chemistries, and are also capable of beingupdated through a communication port.

While the various embodiments of the invention are described withreference to a mechanical compressions device, those skilled in the artwill immediately appreciate that those embodiments are not to be limitedto powering such a device. Indeed, such a use is merely exemplary, and abattery in accordance with the various embodiments of the presentinvention may be used to power any device, and in particular, medicaldevices, wherein the design requirements of the device are met by thecapabilities of such a battery.

When a battery in accordance with the various embodiments of the presentinvention is used with a mechanical compression device, the battery mustbe capable of powering the mechanical compression device for long enoughto treat the patient not only in the field, but also during transport ofthe patient from the field to a care center. Experience has shown,however, that a patient's size and weight are factors that determine theamount of current drain on the battery during treatment. Accordingly,treatment of a larger than average patient results in a larger currentdraw on the battery.

For example, studies have found that the chest depth, chest breadth andchest circumference are factors influencing the amount of current drainon a battery powering a mechanical compression device. Other studieshave observed that the mean chest depth of an average adult human maleis 9.4 inches, mean chest breadth is 12.2 inches and mean chestcircumference is 39.7 inches. See, Young, J W, R F Chandler, C C Snow, KM Robinette, G F Zehner, M S Lofberg, Anthropometric and MassDistribution Characteristics of the Adult Female, FAA Civil AeromedicalInstitute, Okalhoma City, Okla., Report No. FAA-AM-83-16, 1983;Anthropometry and Mass Distribution for Human Analogues: Volume 1:Military Male Aviators, Report No. USAFSAM-TR-88-6, March, 1988;Haslegrave, C M, “Characterizing the anthropometric extremes of thepopulation”, Ergonomics, 29:2, pp. 281-301, 1986; Diffrient, N, A RTilley, J C Bardagy, Human Scale 1/2/3, The MIT Press, Cambridge, Mass.,1974; and PeopleSize Pro Software, Open Ergonomics Ltd., 34 BakewellRoad, Loughborough, Leicestershire, LE11 5QY, United Kingdom, theentireties of which are hereby incorporated by reference herein. Abattery that can sustain operation of the mechanical compression devicefor at least thirty minutes for an average size patient, and at leasttwenty minutes for a larger than average size patient is advantageous.

Referring now to the drawings in detail, in which like referencenumerals indicate like or corresponding elements among the severalfigures, there is shown in FIG. 1 a chest compression belt fitted on apatient 1. A chest compression device 2 applies compressions with thebelt 3, which has a right belt portion 3R and a left belt portion 3L.The chest compression device 2 includes a belt drive platform 4 and acompression belt cartridge 5 (which includes the belt). The belt driveplatform includes a housing 6 upon which the patient rests, a means fortightening the belt, a processor and a user interface disposed on thehousing. The belt includes pull straps 18 and 19 and wide loaddistribution sections 16 and 17 at the ends of the belt. The means fortightening the belt includes a motor attached to a drive spool, aroundwhich the belt spools and tightens during use. The design of the chestcompression device, as shown herein, allows for a lightweightelectro-mechanical chest compression device. The fully assembled chestcompression device weighs only 29 pounds, and is thus hand-portable overlong distances. The device itself weighs about 22.0 to 23.0 pounds, withthe battery, in at least one embodiment of the present invention,weighing between 2 and 5.0 pounds, and preferably about 3 pounds. Thebelt cartridge weighs about 0.8 pounds and the straps to secure thepatient weigh about 1.6 pounds.

FIG. 2 shows the posterior side 23 of the chest compression device asseen from the superior direction. In the perspective of FIG. 2, theaverage sized patient's buttocks and the back of the patient's legswould extend past the inferior bumper 40. The device is built around asturdy channel beam 41 that is laterally oriented with respect to thehousing. The channel beam supports the device against the forces createdduring compressions. The channel beam also serves as the structure towhich the belt cartridge is attached.

The channel beam 41 forms a channel extending across the lateral widthof the device. During compressions, the belt is disposed in and travelsalong the channel. The belt is attached to a drive spool 42 that spansthe channel.

FIG. 3 shows internal components of the chest compression device 2. Amotor 79 is operable to provide torque to the drive spool 42 through aclutch 80 and a gearbox 81. A brake 82, attached to the superior side ofthe motor, is operable to brake the motion of the drive spool. The brakehub connects directly to the rotor shaft of the motor.

The motor 79 and brake 82 are controlled by a processor unit 83, motorcontroller 84 and power distribution controller, all of which aremounted to the inside of the anterior cover plate 60. The processor unitincludes a computer processor, a non-volatile memory device and adisplay.

The processor unit is provided with software used to control the powercontroller and the motor controller. Together, the processor unit, powercontroller and motor controller make up a control system capable ofprecisely controlling the operation of the motor. Thus, the timing andforce of compressions are automatically and precisely controlled forpatients of varying sizes.

FIGS. 2 and 3 also show the location of a battery compartment 121 nearthe head of the patient. The location and design of the battery pack andbattery compartment allow for rapid exchange of batteries. A spring inthe back of the compartment forces the battery pack out unless thebattery pack is fully and correctly inserted in the compartment. A latchon one end of the battery pack engages a receiver in the batterycompartment 121 to hold the battery pack within the batter compartmentwhen the battery pack is inserted into the battery compartment. Recesses120 indicate the location of the springs inside the battery compartment121. Plastic grills 122 at the end of the battery compartment reinforcethe recesses.

FIGS. 4A and 4B are perspective views of a battery pack 200 showing thefront and back sides 205, 210 of the battery pack respectively. Frontside 205 of the battery pack faces outward and is visible to the userwhen the battery pack is inserted into the battery compartment 121 (FIG.3). As shown in FIG. 4A, front side 205 includes a latch 215 thatengages a receiver within battery compartment 121 to hold the batterypack 200 within the battery compartment. Also shown in FIG. 4A are apair of raised tabs 217 disposed on the tops side of the front end ofthe battery pack. These tabs cooperate with the latch to ensure that thebattery is properly seated in the battery compartment by prevent the topof the battery from riding up during battery insertion, forcing thelatch into proper engagement with a battery latch receiver or lip of thebattery compartment.

The back side 210 of the battery pack, as seen in FIG. 4B, includes aconnection 220 that connects to a connector within battery compartment121 to enable electrical communication between the controller orprocessor of the mechanical compression device and the battery pack 200.This connector not only allows for the flow of current from the batterypack to power the mechanical compression device, but it also providesfor the flow of data, programming commands and other information, suchas battery charge status, discharge rate, time remaining untildischarged, and the like between the battery pack and the processor orcomputer controlling the operation of the mechanical compression device.Similarly, connector 220 may be configured to be connected to aconnector in a battery charger to charge the cells of the battery pack,as well as to provide for the flow of data, software programs orcommands and/or other information between the charger and the batterypack. It is also contemplated that connector 220 may be used to connectthe battery pack to a communication network that would allow for flow ofinformation between the battery pack and other computers, servers,processor or devices that are also connected to the network. It will beunderstood that the network may be a wired network, such as, forexample, an Ethernet, or it may be a wireless network. The network maybe a local network, or it may be a wide area network, such as a WLAN orthe Internet.

A status indicator 225, which may be, for example, one or more lightemitting diodes (LEDs) or similar devices, is also disposed on the backend 210 of battery pack 200 to provide a visual indication of, forexample, the charge/discharge status of the battery pack, the presenceof any faults that would affect the operation of the battery pack, orother information that might be useful to the user of the battery. Apush button 230 is also included; button 230 may be used, for example,to initiate a reset of the battery pack. Alternatively, button 230 maybe used to initiate a diagnostic test, the results of which may beindicated by status indicator 225. In other embodiments, pressing button230 may initiate other functions of the processor in the battery pack,including, for example, and not by way of limitation, determining theremaining capacity of the battery, display of fault codes through theuse of status indicator 225 and the like.

FIG. 5 is an exploded perspective view of the battery pack 200. Thebattery pack 200 in this exploded view has been inverted from the viewof FIGS. 4A and 4B. The battery pack has a bottom enclosure 234 and atop enclosure 232. A battery latch assembly having a battery latch 236,a lever base 238 and a lever latch 240 is mounted at the side of thebattery pack facing outward when the battery pack is inserted into abattery compartment, and is held in place by the bottom and topenclosures. Lever latch 240 has a wing 241 that is inserted into agroove or slot 243 formed in a face of battery latch 236, and lever base238 is mounted on the bottom enclosure to pivotally hold lever latch 240in the enclosure. Compression springs 254 are disposed between a bottomend of battery latch 236 and top enclosure 232. A projection 255 isdisposed a top end of battery latch 238, and is configured to protrudethrough slot 251 that extends through a thickness of the bottomenclosure 234. In this manner, battery latch 236 may be manipulated by auser to engage and disengage projection 255 from the latch receiverlocated in the mechanical compression device to insert the battery packinto the battery compartment and to release the battery pack for removalfrom battery compartment 121.

Disposed at the back end 210 of the battery pack is a battery entryboard 242 to which is mounted connector 220, indicator 225 and button230 (FIG. 4B). Entry board 256 is mounted to bottom enclosure 232 usingone or more screws 250. The entry board may also be fastened to topenclosure 252 using one or more screws 256. In some embodiments, a waterresistant gasket 262 may be used to resist the incursion of fluids intothe interior of the battery pack. Moreover, a label 260 may be used toprovide information to a user relative to the various indications thatmay be provided by indicator(s) 225.

A battery management board 244 to which is mounted processors, memoryand electrical circuitry for managing the various operations of thebattery (which is described in more detail below) is mounted usingscrews or other fasteners 258 to battery cell assembly 246. Battery cellassembly 246 includes one or more battery cells 248. Battery cells 248may be cells utilizing a variety of battery chemistries, such as, forexample, nickel metal hydride, lithium hydride, lithium-ion and thelike. Battery management board 244 and battery cell assembly 246 mayalso include a pair of splatter shields 266 mounted on left and rightsides of battery cell assembly 246 to protect the terminals of theindividual battery cells 248 from inadvertent contact with other partsof the assembly, thus providing a shield against short circuit of thebattery cells.

Battery pack 200 also includes at least one vent 264, shown disposed inthe top enclosure to allow for venting of the battery pack to preventbuildup of potentially flammable or explosive gases produced by thebattery cells 248 during charging or discharging of the battery pack.While shown disposed in the top enclosure, those skilled in the art willappreciate that the vents may be disposed through any wall or side ofthe battery pack. Vents 264 may be a simple hole extending through thewall or side of the battery pack. Alternatively, vent 264 may include afiltering means 265, such as a screen or hydrophobic membrane to preventthe incursion of particulates or fluids or moisture into the interior ofthe battery pack. An additional advantage of such vents is that the ventor vents provide for equalization of pressure between the interior andexterior of the battery pack, such as may occur when the battery pack istransported to a higher or lower altitude.

The mechanical compression device described above requires a reliablepower source to operate. It is not unusual for the device to be requiredto be used for thirty minutes or more to provide resuscitation to apatient in an emergency. The torque and power requirements of the motorof the mechanical compression device require up to a peak of seventyamperes of current during compression. If enough current cannot bedelivered by the battery to the motor controlling the compressions, thevoltage falls off and the motor may not be capable of generating enoughtorque to ensure complete compression of a patient's chest.

The inventors of the present invention have realized that having a verylow total internal resistance is key to ensuring extended and reliableoperation of the battery when the battery is under a constant powerdrain. One such battery chemistry that has been found to be useful indevices requiring high power is a battery using Lithium Ion chemistry,such as the model ANR26650M1-A or ANR26650M1-B Lithium Ion cellavailable from A123 Systems, Incorporated.

FIG. 6 is a schematic diagram illustrating one embodiment of a batterypack 300 in accordance with the present invention. Battery pack 300includes eleven Li-Ion chemistry cells, such as the model ANR26650M1-Aor ANR26650M1-B cells described above. Each cell provides 3.3 volts, andthe eleven cells are connected in series to provide a total of 36.3volts. Using such cells, one embodiment of a battery pack in accordancewith principles of the present invention can be manufactured that weighsapproximately three pounds. Such a battery has been observed to deliverbetween 1550 and 2000 watts, and preferably deliver a peak power of 1800watts. This provides a desirable weight to power ratio. Moreover, suchan embodiment has also been found to be able to deliver energy ofslightly less than 100 watt/hours. While eleven battery cells are usedin this exemplary embodiment, more or less cells could be used dependingon the requirements of the device to be powered.

To provide the amount of current required to operate the motor of thecompression device, the inventors have discovered that it is importantto minimize the internal resistance of the battery pack. Accordingly,the Lithium Ion (Li-Ion) cells used should have low internal DCresistance, preferably below 15 milliohms, and more preferably below12.5 milliohms per cell.

While Li-Ion batteries are capable of providing the voltage and currentrequired to operate a mechanical compression device for extended periodsof time, care must be taken during both the discharge phase, andrecharge of the batteries to ensure that the batteries continue tofunction for their desired lifetimes. It is well known that Li-Ion cellsshould not be over charged, nor should they be over discharged.Accordingly, various embodiments of the present invention include thecapability of monitoring and controlling both the discharge of the cellsand the recharging cycle. Those embodiments will be discussed in moredetail below.

As described previously, the eleven Li-Ion cells 310 are connected inseries by a main power bus 320. Bus 320 has both a positive side and anegative, or ground side, as is typical for a DC circuit. Bus 320delivers the direct current provided by the battery cells to a load (inthis example, the mechanical compression device) through an interface330. As shown in FIG. 6, interface 330 is a pin connector having sevenconnection pins. Alternatively, a socket could be used, or a combinationof pins and sockets, with more or less than seven pins or sockets couldbe used.

The positive side of bus 320 is connected to pin 7 of interface 330.Similarly, the negative side of bus 320 is connected to pin 6 ofinterface 330. Pins 1-5 of interface are used to communicate varioussignals involved in the monitoring and control of the battery pack, aswell as for communication to the device that is being powered, enablingthe exchange of information and control signals between the battery packand the powered device. Various exemplary embodiments of the inventionincorporating those features will be discussed in more detail below.

Returning again to FIG. 6, the positive side of bus 320 includes a fuse342 to protect the circuit from over current conditions. Fuse 342 maybe, for example, a 30 ampere fuse. In such a case, a sustained currentflow through fuse 342 of more than 30 amperes would cause the fuse toopen, breaking the circuit created by bus 320 and stopping the flow ofcurrent from the battery cells. While not shown, there is also a blownfuse detector circuit that monitors the fuse, and, if the fuse is blown,provides a signal to the pack controller that the fuse is blown. Thepack controller may then provide a signal indicating that the battery isnot suitable for use. Such a signal, for example, may be the change incolor of and LED, or activation or de-activation of some other statusindicator. Alternatively, the pack control may provide a signal to theequipment powered by the battery, which may then provide an indicationto a user that the battery is not ready for use.

The positive side of main bus 320 also includes a number of n-channelfield effect transistors (n-FET) 340, 350 and 360. These n-FETs providefor switching and control of the circuit. N-FETs are used because theyprovide a very low resistance switch in keeping with the designrequirement of minimizing the total internal resistance of the battery.Another unique capability of the n-FET is that they are capable ofconducting high current loads, without damage and without generatingexcessive amounts of heat. One example of an n-FET that has been foundsuitable for use in various embodiments of the present invention is themodel IRLS3036, available from Digi-Key Corporation.

In typical designs, p-FET devices would be used as the switches andwould be placed in the high side of the main bus. However, p-FETS havetwo or more times the on resistance of an n-FET device. Thus, to handlethe same current as an n-FET device, several p-FETs wired in parallelwould be needed. Moreover, use of several p-FETS may also require theuse of a heat sink to dissipate heat generated while the p-FET is on.This is disadvantageous where space within the battery pack is limited.

Similarly, an n-FET device would typically be used in the low side ofthe main bus to switch the current on and off in the bus. However, useof an n-FET in this situation breaks the ground of the battery, whichmay cause noise in the circuit and interfere with communication betweenthe various elements of the battery management system circuitry.Accordingly, the inventions have placed the n-FET switches in the highside of the bus, which provides efficient switching of the bus withoutthe generation of excess heat that may occur when p-FETs are used.Placing the n-FETs in the high side of the bus also eliminates theproblem of breaking the ground of circuit.

In some embodiments, one or more resistors, such as resistors 370 and380, may be inserted in the negative, or low, side of the main buscircuit. These resistors provide the ability to tap the main bus tomonitor various aspects of the current flowing through the circuit. Forexample, in one embodiment, resistor 370 is connected across the inputlines of a cell balancing and primary protection circuit, which isdiscussed in more detail below. A typical value for resistor 370 is, forexample, 2.5 milliohms.

In another embodiment, resistor 380 may be connected across astate-of-charge monitor, also known as a “gas gauge.” In thisembodiment, the value of resistor 380 may be, for example, 5 milliohms.

Each of the cells 310 is individually monitored during both charging anddischarging to control the rate of charging and discharging,respectively. In one exemplary embodiment, as shown in FIG. 6, aseparate cell tap line 390 is connected to each cell and to a cellmonitoring and balancing circuit 400.

Primary Protection

During charging, the voltage of each cell is independently monitored toprevent overcharging of the cell. In one exemplary embodiment, amonitoring system on a microchip, which may be, for example, batterypack protection and monitor integrated circuit (IC) 410 such as an OZ890available from O₂ Micro, is used to control the charging of the variouscells. In such an arrangement, cell monitoring line 390 provides apositive signal to a representative pin input of IC 410. For example,cell 1 is monitored using input line BC1 of IC 410, and so forth up tocell 11, which is monitored using input line BC11 of IC 410.

If the control circuitry of IC 410 detects an imbalance in a cell, IC410 provides a signal on an appropriate external bleed control lineCB1-CB11. As shown in FIG. 6, when the signal on the appropriateexternal bleed control line is applied to the gate of n-FET 420, currentis allowed to pass between the source and the drain of n-FET 420 andthen through resistor 430, which results in bypassing the cell andhalting charging of the cell. As can be seen from FIG. 6, each cell hasits own dedicated combination of resistor and n-FET in electricalcommunication with IC 410 for monitoring each cell and preventing eachindividual cell from over charging.

Cell balancing and primary protection IC 410 may also be used in someembodiments to monitor the total voltage of the battery cell pack. Forexample, when all of the cells have attained their maximum voltage, IC410 can send a low signal to the gate of n-FET 350 to open the channelbetween the source an drain of n-FET 350 and thus open the main buscircuit 320. This results in a cessation of charging current through thecells, and thus halts the charging process.

Similarly, IC 410 monitors the voltage across the cells during dischargeof the battery. When the voltage across the cells drops below athreshold level, for example, 21 volts, IC 410 drives the signal on line450 low, which in turn shuts off n-FET 360 which interrupts the main buscircuit. This prevents damage to the battery cells that may be caused byremoving too much of the charge in the cells, which may result indecreased life of the cell.

IC 410 may also include and control a temperature measurement capabilitydesigned to monitor the temperature of the battery pack and/orindividual battery cells to prevent overheating. In this embodiment, oneor more thermistors 460 are used to provide temperature signals overline 470 to the IC 410. If IC 410 determines that the temperature of thebattery is either too high or too low, IC 410 may drive either or bothof n-FETs 350 and 360 low, opening the main bus 320 and isolating thebattery pack. It will be understood that while only a single line 470 isshown for clarity, line 470 includes an appropriate number of conductorsto monitor the function of all thermistors used in the temperaturemonitoring circuit in communication with IC 410.

IC 410 may additionally provide a visual indication of fault state byproviding a fault signal on line 480 that may then be used to cause LED490 to light up. This visual signal of a fault condition sensed by theprimary protection circuit indicates that the battery pack has beenrendered non-functional by IC 410 and that repair or maintenance of thebattery pack may be required.

Secondary Protection

Some embodiments of the present invention may also include secondaryprotection against catastrophic faults or over voltage protection. Suchsecondary protection may be provided by a variety of circuits designedto monitor the voltage of the battery pack and/or the current flowthrough the main bus and to take action when certain thresholds valuesof current or voltage are exceeded. In one embodiment, such protectionmay be provided by an integrated circuit 500, such as, for example, theOZ8800 available from O₂Micro. Those skilled in the art will know that,depending on the number of cells used in the battery pack, more than oneIC 500 may be required. For example, the OZ8800 secondary level batteryprotection integrated circuit can monitor three to seven individualcells. Thus, where eleven cells are used, two OZ8800s will be required.

IC 500 monitors the voltage of each cell over monitoring line 312. Insome embodiments, a time delay may be employed that provides fortemporary over voltage conditions to exist. Where the time threshold isexceeded because the voltage did not drop back into an acceptable range,IC 500 sends a low signal over fault line 510 to n-FET 340 to turn offn-FET 340. Each cell is monitored by a similar circuit.

It should be apparent from FIG. 6 that the n-FETs described above are ina normally off state unless a positive voltage is applied to the gate ofeach n-FET. Thus, any fault that results in voltage decrease to a levelbelow the threshold of the n-FET at the gate will cause the n-FET toopen, thus providing additional protection to the cells and batterymanagement circuitry.

Gas Gauge

Another embodiment of the present invention includes a “gas gauge”function that monitors the amount of useful charge remaining in thebattery pack. Such gas gauge functionality can be provided usingintegrated circuits designed to carry out vary tasks, such as tocalculate remaining battery capacity for use and standby conditionsbased on time of use, rate of discharge and the temperature of thebattery. Such a circuit may also determine the true battery capacity inthe course of a discharge cycle from near full charge to near fulldischarge states.

FIG. 6 illustrates one example of such a gas gauge circuit 600.Monitoring of the battery pack is accomplished using an integratedcircuit 610, such as a bq2060A available from Texas Instruments, Inc. IC610 works in conjunction with an external EEPROM 620. EEPROM 620 storesconfiguration information for IC 610, such as the chemistry used in thebattery cells, the self-discharge rate of the battery, various ratecompensation factors, measurement calibration, and battery designvoltage and capacity. All of these settings can be changed to allow thesystem to be used with a variety of battery types. Moreover, IC 610 cancommunicate with a central processor and memory over a back-side buscircuit 630. In this manner, IC 610 and EEPROM 620 may be configured,using control signals from the central processor, to accommodatedifferent types of batteries that are detected and identified by othercircuitry included in the system, or which are manually identified by auser. In an alternative embodiment, IC 610 may also cooperate with thepack controller to augment the reporting accuracy of the gas gauge ininstances of low current draw using appropriate control commandsembedded into the software that controls the operation of the packcontroller and the gas gauge to implement the algorithms necessary tocarry out this function.

In general, the gas gauge functions are carried out by IC 610 inconjunction with IC 800 to determines full charge battery capacity andthe capacity remaining at any point in time by monitoring the amount ofcharge input or removed from the battery cells. In addition, IC 610measures battery voltage, battery temperature and current as detectedacross resistor 380. IC 610 also, in some embodiments, may estimate theself-discharge rate of the battery, and also monitors for low-voltagethresholds of the battery. As described, IC 610 measures the amount ofcharge and discharge of the battery by monitoring the voltage acrossresistor 380, which is located between the negative terminal of thefirst cell 310 (of the series connected cells) the negative terminal ofthe battery pack. Available battery charge is determined from thismeasured voltage and correcting the measurement for environmental andoperating conditions.

IC 610 may also measure the temperature of the battery pack so as tocarry out the estimations and adjustments described above. In oneembodiment, a thermistor 640 is mounted adjacent to a cell or cells ofthe battery pack in such a manner as to be able to measure thetemperature of the cell or cells of the battery pack. IC 610 drives thegate of n-FET 650 high by providing an appropriate signal over line 660to connect a bias voltage source to thermistor 640 while the temperatureof the cell or cells is being measured. Once the measurement iscompleted, IC 610 drives the gate of n-FET 650 low, opening the n-FETand thus disconnecting thermistor 640 from the bias source.

IC 610 may be reset each time the battery is charged so that thereported amount of charge remaining in the battery is accurate. Abattery pack supervisor circuit or pack controller 800, to be describedin more detail below, provides a signal over reset line 670 to drive thegate of n-FET 680 high. This causes the current to flow through n-FET680, resulting in a reset signal being provided to IC 610 to reset thebattery capacity counter of IC 610.

In another embodiment, IC 610 may include a seal/unseal function thatprevents unauthorized access to the parameters stored in the IC 610 orEEPROM 620. Pack controller 800 may send a signal over line 680 thatdrives the gate of n-FET 690 high, which closes n-FET 690 allowing forcommands and data to flow between IC 610 and EEPROM 630. Such data mayinclude, for example, updated calibration information and the like. Inan alternative embodiment, the flow of data between IC 610 and EEPROM630 may be controlled using only software commands from the packcontroller to control IC 610 and EEPROM 630 without requiring n-FET 690.

Pack Controller

In another embodiment of the present invention, the battery managementsystem includes a pack controller 800 which serves as an overallsupervisor for the various functions carried out by the batterymanagement system. Pack controller 800 will typically be an integratedcircuit, although discrete circuitry carrying out the same functionscould be used, depending on the amount of space available within theconfines of the battery pack.

For example, pack controller 800 may be a low or ultra-low powermicrocontroller such as the MSP430F2418 Mixed Signal Controlleravailable from Texas Instruments Incorporated. Such a controller mayinclude memory, such as random access memory or flash memory to providefor rapid and efficient execution of the various functions of thebattery management system. Pack controller 800 also has the capabilityof communicating with peripheral devices, circuitry or memory over oneor more communication buses, such as backside bus 630 and front-side810. The communication busses typically use a communication protocolsuch as, for example, the I²C bus (a Trademark of Philips Incorporated)or the System Management Bus (SMBus). The SMBus is described in moredetail below.

Appropriate software commands are used to program the functions of thepack controller 800. Such software includes commands configuring thecommunication protocol interface, such as for example, the SMBusinterface. The software would also configure the pack controller tomonitor critical battery pack parameters, which are made available to itover communication lines 810, 820, 822, back-side bus 630, front sidebus 810 and detect line 824, as well as other communications lines notshown or which may be added in the future.

When appropriately programmed, pack controller 800 is also incommunication with one or more memory devices, such as, for example, anevent archive EEPROM 900. Such an archive has, for example, although notlimited to, 64 kilobytes of memory that can be used to store history ofvarious events that occur during the charge and discharge cycles of thebattery pack, such as, for examples, the total amount of charge, totalamount of energy discharged, the temperature of the battery cells, anyfaults that occur, or other information related to the individualbattery cells and/or the various circuits employed to manage and controlthe operation of the battery.

Pack controller 800 may also be programmed to communicate with memoryand/or processors such as, for example, EEPROM 1000. In the exemplaryembodiment shown in FIG. 6, EEPROM 1000 may be located in a mechanicalcompression device that is powered by the battery pack, or it may beincorporated into the battery pack and configured to be accessed by thedevices to be powered by the battery. In this example, pack controller800 communicates with EEPROM 1000 and/or a processor in the mechanicalcompression device over front side bus 810, which accesses a similar busin the mechanical compression device through connector 330. In thismanner, a two-way communication connection may be established betweenthe battery pack and a device powered by the battery pack to allow forexchange of information between the battery pack and the powered device.For example, updated operating parameters or commands, including updatedsoftware, may be loaded into the battery pack from the powered devicewhen the battery pack is put into communication with the powered device.Similarly, information contained in the event archive EEPROM 900 may betransmitted to the EEPROM 1000, or any other memory (such as a portablememory device) configured for communication over back-side bus 810 fromany of the memories present in the battery pack.

It will be understood that this communication capability also allows thebattery to communicate with other devices besides devices which will bepowered by the battery. For example, typically, the battery pack will beremoved from a powered device to be recharged. When the battery pack isconnected to a battery charger, the battery charger may be used toretrieve information from the memory or memories of the battery pack,and/or transmit updated data, information, programming commands orsoftware to the battery through front-side bus 810. This communicationprocess will typically be managed using various handshaking andcommunication dialog as set forth in the communication protocol used toenable the communication, such as the SMBus protocol, exchanged betweena processor residing in the charger or other device and the packcontroller 800 of the battery pack. In some embodiments, the battery mayalso be trickle charged when the battery is inserted into the device tobe powered, where the device being powered is also connected to anexternal power supply.

Still other embodiments of the present invention may include acapability, managed by pack controller 800, of recognizing when thebattery pack is inserted into a battery charger or device to be powered,such as a mechanical compression device. For example, pack controller800 may be configured using appropriate software and/or hardwarecommands to provide a signal to IC 410 and IC 500 to provide a highsignal to the gates of n-FETs 340, 350 and 360 to close those switchesand thus provide full battery voltage at the positive and negative pinsof connector 330 only when detect circuit 1100 sends an appropriatesignal to pack controller 800 over line 824 indicating that the batterypack is properly mounted into a device to be powered.

In one embodiment, pack controller 800 monitors a line connected to amechanical switch or interlock that is forced closed when the battery isproperly inserted into a charger or a device to be powered. In anotherembodiment, pack controller 800 monitors a signal line connected to oneor more pins of the battery connector. When an appropriate signal isreceived over this signal line, pack controller 800 determines that thebattery is inserted into a charger or a device to be powered, andprovides a high signal to the gates of n-FETs 340, 350 and 360 asdescribed above. This embodiment is particularly advantageous in thatpack controller 800 may be programmed to respond only when a particularsignal is received, ensuring that the battery is inserted into aspecific type or make of a charger or device to be powered designed toaccommodate the battery before providing the high signal to the gates ofn-FETs 340, 350 and 360.

These embodiments are advantageous in that discharge of the battery inthe event of an accidental short circuit across the positive andnegative terminals of connector 330 is prevented. Given the amount ofenergy stored in the cells of the battery pack, such a discharge couldbe catastrophic. Thus, in this embodiment, there is no voltage betweenthe positive and negative terminals of connector 330 of the battery packunless the battery pack is properly mounted in a device configured toprovide the appropriate signal to the detect circuit 1100, thusproviding for safe handling, storage and transport of the battery backwhen the battery pack is not connected to either a charger or a deviceto be powered, such as the mechanical compression device describedabove.

Pack controller 800 may also be programmed to provide password access toallow for changing of settings and parameters stored in EEPROMs 900 and620, as well as to provide appropriate signals to drive LED 490 in theevent of a fault. Additional capabilities may also be included,configured using appropriate software and/or hardware commands, toprovide additional functions to the battery management system. Forexample, such functions may include driving a display that indicates thetotal amount of charge remaining in the battery and the like. A morecomplete description of the various capabilities that can beincorporated into pack controller 800, particularly when pack controller800 is an MSP430F2418 (or other members of this controller family) iscontained in a document entitled “MSP430F241x, MSP430F261x Mixed SignalMicrocontroller,” SLAS541F—June 2007—Revised December 2009 availablefrom Texas Instruments Incorporated, the entirety of which is herebyincorporated herein by reference.

Smart Bus Communications

As will be apparent, the various processors and integrated circuits andlogic systems incorporated into the various embodiments of the presentinvention are capable of functioning as a unified system due to theirability to communicate with one another over the front side bus 320 andthe back side bus 630. In some embodiments, the communications overthese buses are carried out using the System Management Bus (SMBus)specification. The SMBus is a two-wire interface through which varioussystem component chips, such as IC 410, IC 610, the secondary protectionsystem 500, event archive 900, EEPROM 1000 and pack controller 800,among other circuitry, can communicate with each other and with the restof the system. Further information related to the SMBus specification iscontained in “System Management Bus (SMBus) Specification Version 2.0,”SBS Implementers Forum, Aug. 3, 2000, the entirety of which is herebyincorporated herein by reference.

Boost Circuit

The inventors have observed that, in some embodiments of the invention,the voltage required to drive the n-FETs closed exceeds the voltage thatis available from the battery pack. For example, using an n-FET thatrequires a bias voltage of 10 volts, the n-FET requires a drive voltageof the bias voltage plus the battery voltage to drive the n-FETsufficiently to allow an appropriate voltage to pass through the n-FETto charge or discharge the battery. Accordingly, a voltage boost circuitis included to boost the voltage supplied to the gates of the n-FETs todrive the n-FETs to conduct the current supplied by the battery cells.

Those skilled in the art will understand that the use of n-FETs in thepresent invention results in the need for complex circuitry, such as theboost circuit. Such complexity could be eliminated using p-FETs. Use ofp-FETs however, has been found to be disadvantageous because severalp-FETs may be needed to handle the same current that can be handled by asingle n-FET. Additionally, the heat generated using multiple p-FETs mayrequire the addition of one or more heat sinks to dissipate the heat,which may require more space in a compact battery than which isavailable. Moreover, it is well known that p-FETs have at least twicethe on resistance of n-FETs, which would increase the overall internalresistance of the battery pack.

Archive Memory

Referring again to FIG. 6, pack controller 800 is in communication withevent archive EEPROM 900. In one embodiment, event archive EEPROM 900 isa non-volatile memory device, such as a flash memory device, having, forexample, 64 kilobytes of memory capacity. As described previously, thepack controller 800 may store data and information related to usage,operation and performance of the battery pack in event archive 900 forlater retrieval and analysis.

Table 1 is an exemplary listing of data or information related to thelong term history of the battery that may be sensed or collected by packcontroller 800 during the lifetime of the battery and then stored in theevent archive 900. It will be understood that while certain fields areshown, other data fields may be used, depending only on the designrequirements of the system.

TABLE 1 Size Size Address Address Data Field (Byte) w/CRC Unit OffsetStart Offset End Battery Clock 4 5 sec 0 4 Number of charges starting at2 3 5 7 FCC >= RC > FCC-250 Number of charges starting at FCC- 2 3 8 10250 >= RC > FCC-500 Number of charges starting at FCC- 2 3 11 13 500 >=RC > FCC-750 Number of charges starting at FCC- 2 3 14 16 750 >= RC >FCC-1000 Number of charges starting at FCC- 2 3 17 19 1000 >= RC >FCC-1250 Number of charges starting at FCC- 2 3 20 22 1250 >= RC Unused1 1 23 23 Maximum lifetime FCC 2 3 mAh 24 26 Minimum lifetime FCC 2 3mAh 27 29 Maximum lifetime load test voltage 2 3 mV 30 32 Minimumlifetime load test voltage 2 3 mV 33 35 Maximum lifetime load testcurrent 2 3 0.01 A 36 38 Minimum lifetime load test current 2 3 0.01 A39 41 Maximum lifetime load test power 2 3 Watt 42 44 Minimum lifetimeload test power 2 3 Watt 45 47 Maximum lifetime peak charge 2 3 0.1 4850 temperature Kelvin Maximum lifetime peak charge 1 2 51 52 sensorIdentification Minimum lifetime peak charge 2 3 0.1 53 55 temperatureKelvin Minimum lifetime peak charge 1 2 56 57 temperature sensorIdentification Maximum lifetime peak discharge 2 3 0.1 58 60 temperatureKelvin Maximum lifetime peak discharge 2 3 61 63 temperature sensorIdentification Lifetime low power count 1 2 64 65 Lifetime full chargecycle count 2 3 66 68 Lifetime condition cycle count 2 3 69 71 Lifetimewakeup count 1 2 72 73 Lifetime reset count 1 2 74 75 Lifetime totalfault count 2 3 76 78 Lifetime cell under-voltage count 1 2 79 80Lifetime over-current fault count 1 2 81 82 Last condition cycle time 45 sec 83 87 Charge cycle count during last 2 3 88 90 condition cycle

Abbreviations used in the Table 1 are identified as follows: CRC meanscyclic redundancy check; FCC means full charge capacity; RC meansremaining capacity.

Referring to Table 1 above, the clock field may be updated whenever thebattery's runtime archive is changed. In case the battery loses powercompletely, the battery can use this field to reset its clock to thelatest recorded time. This ensures that the timestamp in all historyrecords stored in the memory increases with time, even after a powerloss, to facilitate reassembly of the complete history data downloadedfrom the battery memory. Although it is not possible to account for thetime lapse during a power loss, the time lapse may be estimated from thegap in the timestamps of individual history records. The clock field mayalso be updated using data received from global position satellites, inthose embodiments where a GPS receiver, or other similar technology,such as location technology based on cellular telephone technology, isincluded in the battery.

In one embodiment, the data and information stored in the battery,besides being related or representative of data related to the long termoperation of the battery and are not date sensitive, may also be relatedto run-time events that are recorded as they occur. For example, data orinformation related to an actual use of the battery may be recorded.

In another embodiment of the present invention, the data and informationstored in the battery may include data related to the current operationof the battery. Such data and information is commonly referred to as“run time” information or data.

Table 2 is an exemplary listing of data or information related to thecurrent operation, or run time, history of the battery that may sense orcollected by pack controller 800 during the lifetime of the battery andthen stored in the event archive 900. It will be understood that whilecertain fields are shown, other data fields may be used, depending onlyon the design requirements of the system.

TABLE 2 Total Parameter Length Event ID Parameters/Units (bytes) Batteryheart beat 0 none 0 Error 1 error code  2+ Powered device 2 current @max power, 0.01 A 8 operation power voltage @ max power, mV drain Maxbattery temp, 0.1 K RC, mAh Mode change 3 Mode 7 voltage, mV RC, mAhARC, mAh Battery state at 4 FCC, mAh 7 start of charge RC, mAh voltage,mV charge cycle type Battery state at 5 FCC, mAh 9 end of charge RC, mAhvoltage, mV Peak Temp, 0.1 K Peak Temp ID Load test result 6 voltage, mV7 current, 0.01 A BCP rev # test result BCP update 7 old BCP rev # 4 newBCP rev # Initialization 8 minor software revision 2 complete majorsoftware revision

The run time information and data stored in the EEPROM 900 may be storedin a predetermined format. Once example of such a format, used to storethe data listed in Table 2, is shown in Table 3 below:

TABLE 3 Byte/Unit 1-4 5 6 7-15 16 Data Timestamp, sec Event ParametersParameter(s) CRC field ID total length, byte

In this exemplary embodiment, a data record 16 bytes long is constructedusing the data and information listed in Table 2. Additionally, therecord includes a timestamp, stored in seconds, for each recorded event.

Referring again to Table 2, when an “error” event is detected, theparameter stored in the data record is a 2 byte long error code. Such acode may be useful when the data is analyzed in troubleshooting theerror in operation of the battery or the device being powered anddetermining any correction that needs to be made to prevent the errorfrom occurring in the future. Additional data may be included as neededdepending on the fault detected.

The error code may also be the result of a self-test performed on thebattery systems by the battery management system pack controller 800, orone of the other processors resident in the battery management system.Such a self-test may be initiated either automatically, such as in theevent of a detected problem, or according to a predetermined schedule,or in response to a command from a user.

Various testing is done during the self-test. For example, the processormay test the various functions of the components of the batterymanagement system and/or the battery cells to determine if they arefunctioning within acceptable parameter rangers. In one example, thetemperatures sensors measuring the temperature of the battery or ofindividual battery cells may be polled periodically, such as, forexample, every thirty (30) seconds. The results of the self-test may berecorded in EEPROM 900 as described above. Additionally, the packcontroller 800 may provide a visual indication of the results of test bysending a signal to the battery charger or device being powered tocontrol an indicator or a display. A visual indication may also beprovided by sending a signal to the LEDs of the battery pack. In theevent of a failed test, the pack controller 800 may control the n-FETsof the battery management system to open the main bus, effectivelyturning the battery off. Such a condition may require removal of thebattery from the powered device or charger and insertion (orre-insertion) into a battery charger before controller 800 will allowthe battery to provide current to a device.

The “powered device operation power drain” event is recorded while thedevice to be powered is in active operation. Using this parameter, thebattery monitors the power and writes the current, voltage andtemperature associated with the peak power provided by the battery,along with the remaining charge in the battery, as determined by the gasgauge, to the archive in 5-minute intervals. Each of these parametersrequires two bytes of the data record, for a total of eight bytes.

The “mode change” event provides a record of each time the operatingmode of the battery is changed, along with the battery voltage andremaining charge available at that time. For example, the Mode parameterrequires one byte, with the following modes defined as 0=Not in device,1=In Device, and 2=Low power. “Low power” mode occurs when the packcontroller 800 disables the battery because the power remaining in thebattery has fallen to an extremely low level. The battery also entersthis mode when the pack controller 800 wakes up after losing power, mostlikely during a wakeup charge. Once the battery has enough charge toresume normal operation, controller 800 provides a signal indicatingthat the battery is now in the “In Device” mode. The battery voltage,remaining capacity and adjusted remaining capacity of the battery asdetermined by the gas gauge each require two bytes, for a total of sevenbytes for this event. The adjusted remaining capacity is adjusted forscale, offset and time the battery has been inactive.

The “battery state at start of charge” event requires seven bytes and iswritten when charging of the battery is initiated. The type of chargecycle initiated is recorded in one byte, where 0=normal cycle and1=condition cycle. A condition cycle is initiated when the battery isfirst charged, or after a deep discharge. The battery voltage at thestart of charge, as well as the full charge capacity and remainingcharge in the battery, as determined by the gas gauge, each require twobytes for a total of seven bytes. In the event that a wakeup charge isrequired to resuscitate the battery, the data in this field will berecorded in EEPROM 900 when the battery voltage is sufficient to powerup pack controller 800.

The “battery state at end of charge” event is similar to the “batterystate at start of charge” event, except that it is the battery voltage,full charge capacity, peak battery temperature, peak temperature ID, andremaining charge that is stored. Both the full charge capacity andremaining charge are acquired from the gas gauge. In the event thatcharging is interrupted for any reason, such as, for example, thebattery is withdrawn from the charger before charging is complete, thisevent is not written to EEPROM 900. This event requires a total of ninebytes in the data record.

The “load test result” event records the result of a test that isperformed on the battery by the charger when the battery is in thecharger. The results of the test are recorded in EEPROM 900 by thebattery charger over communication line 810. This record includes onebyte recording the result of the test, such as, for example, where0=Fail, 1=Pass, and 2=Pass with an end-of-life warning. The end-of-lifewarning is an indication that the battery is approaching its servicelife, and may need to be replaced soon.

The “BCP event” is recorded when a new battery configuration parameter(BCP) is uploaded to the battery. The battery configuration parameterincludes fields for revision number and a flag that identifies thedirection of data flow; that is, data flowing into, or out of, thebattery. In some embodiments, the BCP also includes test criteria forcontrolling the load test.

If the upload fails verification, the new BCP will not be saved into thememory of the battery, and this event will not be generated, and thusthis event will not be stored in the EEPROM 900. This event requires atotal of four bytes, with two bytes reserved for the revision number ofthe old BCP stored in the battery before the upload, and two bytesreserved for storing the revision number of the new BCP that has beenuploaded, verified and stored in the memory of the battery.

The “initialization complete” event is recorded upon the completion ofthe first initialization of the battery to record the version of thesoftware loaded into the battery. This event records whether thesoftware revision is a minor or major revision, and is recorded onlyonce in the battery's lifetime, since a software revision will causethis event to be overwritten with the new software version.

Data identifying the battery, such as a serial number or collection ofalpha numeric characters may also be stored in the EEPROM 900, or inother memory associated with the various processors or circuits of thebattery management system. This identification information may be usefulwhen the data is retrieved from the memory and analyzed.

As discussed above, in an embodiment of the present invention, the packcontroller 800 may be programmed to accept data provided to it throughthe front side, or smart bus, 810 by either a battery charger, or adevice which is being powered by the battery. The device to be powered,for example, the mechanical compression device described above, may havea processor and communication system that can transmit data orinformation to the battery that is related to the actual use of themechanical compression device. The battery would then be used as acarrier of the information, which could then be retrieved from the eventarchive memory when the battery was recharged or serviced.

FIG. 7 is a schematic illustration of one such system. In thisillustration, a battery 1300, having data and information stored withinan event archive EEPROM memory, is inserted into a charger 1310 forrecharging after use. Charger 1310 includes a processor 1330 which is inoperable communication with a memory 1320 and a communication circuit orport 1340. When battery 1300 is inserted into the charger, the processor1330 sends a data retrieval request to the pack controller of thebattery to retrieve data and/or information from the event archivememory of the battery. Upon this request, a communication session may beestablished between the processor 1330 and the pack controller of thebattery, wherein the data and/or information stored in the event archiveof the battery is communicated to the processor 1330 of the charger.Alternatively, the pack processor 800 controlling the operation of thebattery may be programmed to transmit the information to a centralserver.

The data and/or information communicated to the processor 1330 may bethen be stored in memory 1320 of the charger. It will be understood thatmemory 1320 may be any storage media that is capable of being written toand read by a processor, and may preferably be a non-volatile memorysuch as flash memory or it may be a storage media such as a hard diskdrive.

Alternatively, processor 1330 may also communicate the retrieved dataand/or information to a storage device external to the charger, such asa computer 1350 which in turn has its own memory or storage media, usingthe communication port 1340. In another embodiment, the data and/orinformation retrieved from the battery may be stored in the memory 1320of the charger until such time as the charger is commanded tocommunicate the data and/or information to another computer, server orother system for analysis. In such an embodiment, the charger may becapable of communicating over a wired or wireless network, such as isillustrated by telephone line 1360 using appropriate communicationhardware and software using a modem connected to a computer or thecharger, to communicate the data and/or information to another system,such as a server 1370 located remotely from the charger 1310. While theinvention is discussed in relation to “a server,” those skilled in theart will understand that “a server” also includes systems where theserver functions are distributed among more than one physical “server”units.

Alternatively, the charger may be capable of communicating through aLAN/WLAN 1380, which may be a local area network, a wide area network,the Internet and the like to communicate the data and/or informationretrieved from the battery to server 1370. Such a communication processmay be carried out through a wired system, or with the addition ofappropriate hardware to the charger, such as a network card, wirelessmodem and the like, may be accomplished wirelessly.

Viral Distribution

FIG. 8 illustrates yet another embodiment of the present inventionwherein the battery archive memory is used to facilitate distribution ofupdated data, information, operating parameters and software that isused by the processors of the battery management system to monitor andcontrol the operation of the battery during the battery's lifetime.

Referring again to FIG. 6, battery pack 300 includes various processorsand controllers, such as, for example, pack controller 800, primaryprotection circuit 410, IC 510 and memories such as EEPROM 1000, EEPROM900 and EEPROM 620, among others. The processors are configured tocontrol the operation of the battery, and the memories are configured tostore, among other data and information, operating parameters used tocontrol the operation of the battery and/or software programming that isused to program and control the processor to carry out the tasksrequired by the designers of the software. Additionally, the memoriesmay store information related to or associated with the operatingparameters and/or software, such as, for example, a version numberassociated with a particular version of the parameters or software, orthe memories may also be used to accumulate and store data related tothe usage of the battery or equipment, performance characteristics orsystem configuration of the battery, charger or equipment powered by thebattery, and maintenance data related to the operation of the battery,charger or equipment powered by the battery.

The data stored and transferred by the battery to and from the chargeror equipment powered by the battery may also include historicalinformation related to individual batteries or pieces of equipment thatthe battery has been in communication with, where the data includes anidentifier that allows the data to be analyzed to determine theoperational history and/or performance of the individual battery,charger or piece of equipment. In some embodiments, the data may alsoinclude location data identifying the location of the charger orequipment to facilitate location of the charger and device in the eventthere is a need to locate the charger or equipment.

Examples of equipment powered by batteries that may benefit from thevarious embodiments of the present invention include, but are notlimited to, battery powered medical devices, defibrillators, mechanicalcompression equipment, and any other equipment that is not typicallyconnected by either a wired or wireless communication network yet stillrequire to be tracked and/or updated on a periodic basis to ensure thatthe devices or equipment are operating with the most up to date data,configuration information, performance specifications, operatingparameters and software programming available.

One common element in a system using rechargeable batteries to powerequipment is that the batteries need to be recharged. Often, to saveweight in the equipment using the battery, if the equipment is designedfor portability, the batteries are removable from the equipment so thatthey may be charged outside of the equipment. Thus, the portableequipment is not required to include battery charging circuitry.

The batteries are typically inserted into a dedicated battery chargerfor recharging. In one embodiment of the present invention, the chargerincludes a processor and a memory. The processor is controlled bysoftware commands that may be imbedded in the processor, or they may bestored in a memory and retrieved from the memory by the processor asneeded. Such programming and control schemes are well known to thoseskilled in the art, and will not be described in detail herein.

Utilizing various embodiments of the present invention, a battery mayhave an updated revision of operating parameters or software commandsstored within the memory of the battery. When the “updated” battery isinserted into a charger, the processor of the battery, the charger, orboth, check the version of the operating parameters or software in thememory of the battery with the version that is present in the memory ofthe charger. If the version on the battery is later than the versionstored in the memory of the charger, the memory of the charger isupdated with the updated version of the operating parameters and/orsoftware present on the battery.

Alternatively, if the version of the operating parameters and/orsoftware present in the memory of the charger is later than the versionstored in the memory of the battery, the latter version of the operatingparameters and/or software stored in the charger is downloaded into thebattery. In this manner updated versions of the operating parametersand/or software programs can be propagated across a fleet of batteriesused to power equipment.

In another embodiment of the invention, a battery can be used as acarrier to distribute or retrieve data generated during usage of thebattery and/or equipment. Such data may include, for example and withoutlimitation, historical operational data, maintenance data and the like.

In still other embodiments, one or more of the chargers or pieces ofequipment powered by the battery may be in communication with acentralized network or server through a communication system such as theInternet or other wired or wireless network or communication line. Inthis way, updated data, operating parameters, configuration informationand software programs may be pushed out to the one or more chargersand/or pieces of equipment in communication with the network or serverby, for example, a processor on the network or server suitablyconfigured by appropriate software. Alternatively, the one or morechargers or pieces of equipment may periodically query the network orserver to determine if there are updated data, operating parameters,configuration information and software programs present on the networkor server that need to be downloaded from the network or server to thecharger or piece of equipment, and if so, accept the updated data,operating parameters, configuration information and software programsfrom the network or server and store them in the memory of the chargeror piece of equipment. When a battery is next inserted into the chargeror piece of equipment having the updated data, operating parameters,configuration information and software programs stored in its memory,the updated data, operating parameters, configuration information andsoftware programs is downloaded into the memory of the battery. When thebattery is next inserted into a charger or piece of equipment that doesnot have the updated data, operating parameters, configurationinformation and software programs in its memory, the battery thenuploads the updated data, operating parameters, configurationinformation and software programs to the memory of the charger or pieceof equipment, thus facilitating the rapid distribution of the updateddata, operating parameters, configuration information and softwareprograms throughout the user base of chargers and pieces of equipmentpowered by the battery.

FIG. 8 is a schematic illustration of the use of a battery in accordancewith various embodiments of the invention as a carrier. Updated data,information, or software programming (hereinafter, collectively, “data”)1405 is communicated to a charger 1410. Data 1405 may be communicated tocharger 1410 by a computer in communication with charger 1405.Alternatively, charger 1410 may be connected to a network, server, orother source of data.

In an alternative embodiment, battery A 1415 may contain the data 1405,and communicate the data 1405 to charger 1410 when battery A 1415 isinserted into charger 1410 for recharging. In this embodiment, updateddata 1405 may have been stored in the memory of the battery by aprocessor in powered device 1420 when battery 1415 was inserted into thepowered device, as illustrated by broken line 1425.

Once the data 1405 has been transferred to a memory of charger 1410, thenext battery to be inserted into charger 1410, in this case, battery B1430, may become a carrier for data 1405 if the memory of battery 1430does not already contain data 1405. Assuming that the data 1405 is alater version of earlier data residing in the memory of battery B 1430,the processor of the battery, such as pack controller 800, will controlthe download of the data 1405 from charger 1410 to the memory of batteryB 1430.

When battery B 1430 is inserted into powered device 1420, the processorsof device 1420 and battery B 1430 communicate to determine if the datastored in the memory of device 1420 is an earlier or later version ofthe data stored in the memory of battery B 1430. If the data stored inthe memory of device 1420 is an earlier version, then the data 1405 isuploaded from the memory of battery B 1430 to the device 1420. If thedata stored in the memory of device 1420 is a later version than data1405, then the processors may decide either to download the laterversion of data to battery B 1430, replacing data 1405 with the laterversion for further transmission other devices, chargers and batteries,or the processes may decide that no transfer is to take place, and data1405 is not uploaded into device 1420.

Assuming that battery B 1430 has the latest version of data 1405 storedwithin its memory, the next time battery B 1430 is inserted in acharger, such as, for example, charger 1435, the process is repeated,with processor of battery B 1430 communicating with the processor ofcharger 1435 to determine whether battery B 1430 or charger 1435 has thelatest version of the data. Depending on this determination, the data inbattery B 1430 is either uploaded into the memory of charger 1435, whereit is now available to update the data in other batteries, such asbattery C 1440, or a new version of data will be downloaded from charger1435 into battery B 1430.

Assuming that battery B 1430 has uploaded data 1405 into the memory ofthe charger 1435, the next battery inserted into charger 1435, here,battery C 1440, may again have the data in its memory updated when it isinserted into charger 1435. Battery C 1440 may then transmit updateddata 1405 into powered device 1445 when battery C 1440 is inserted intodevice 1435

This process continues virally, that is, it spreads the updated datafrom charger to battery to powered device in an automated fashion thathelps to ensure that each battery, charger and powered device areoperating using the latest data, information and/or softwareprogramming.

The battery may also include circuitry for determining where the batteryis located, such as circuitry that can communicate with a globalpositioning satellite and analyze the position of the battery from thosecommunications using methods well known in the art. Such locationinformation could then be stored in the event archive memory of thebattery for later analysis and tracking of the location of the battery.

In another embodiment, the battery may also include an accelerometerthat may provide data and information related to the handling of thebattery that can be stored in the archive memory of the battery. Suchdata may be useful in determining the kind and level of forces that thebattery experiences during use and transportation, and may be useful inimproving the design of the battery to prevent damage during use andtransportation to extend the life of the battery. The data gathered fromthe accelerometer may also be used in real time to detect when thebattery or device in which the battery is inserted has been subjected toa shock that may have caused damage to the battery or device to bepowered. In this embodiment, the data is processed by the packcontroller which may determine that the battery should not be used untilthe battery pack is checked for damage. Once a diagnostic test is run,the processor may then, assuming the diagnostic test indicates that thebattery is capable of operating within normal parameters, permit thebattery pack to operate and provide energy to the device to be powered.

In some embodiments, the charger may also exercise and condition thebattery to determine whether the battery's performance is withinacceptable parameters. The battery charger may also include diagnosticprograms which can interface with the battery pack controller to rundiagnostic tests on the battery. In some embodiments, the charger may beconfigured so that the processor of the charger may control the uploadand download of updated operating parameters and/or software or hardwareprogramming commands to the pack controller. The pack controller wouldthen store the updated operating parameters in the appropriate memory,such as EEPROM 620 or to update the programming of the primaryprotection processor 410, the state of charge processor 610 or the packcontroller 800 itself.

Communication of data and information stored within the event archive ofthe battery to an external computer or server for analysis would also beadvantageous in that it would enable the establishment of a battery database. For example, the operation and life of a battery could be indexedby battery serial number, and correlated with data related to the chargeusing a serial number of the charger. Such a database would be useful indetermining long term trends associated with the batteries and chargersas they are used in the field which could then result in the developmentof improvements to the batteries and chargers. Additionally, as upgradesto the operating parameters and/or software or hardware program commandsoccur, the battery history data could be correlated with the upgrades totrack the operational success or failure of the upgrades.

While several particular forms of the invention have been illustratedand described, it will be apparent that various modifications can bemade without departing from the spirit and scope of the invention.

We claim:
 1. A battery pack for powering a device, comprising: arechargeable battery having a positive and a negative terminal; a sensorfor monitoring a parameter related to operation of the rechargeablebattery; a memory for storing a plurality of data related to operationof the rechargeable battery, or data related to an operational parameterof a device being powered by the battery, each data being associatedwith a time stamp derived from a clock value provided by a clock whenthe data is stored in the memory; and a processor powered by therechargeable battery and in electrical communication with the sensor andthe memory, the processor configured to receive signals from the sensorand to store the data related to operation of the rechargeable batteryextracted from the signals from the sensor in the memory, the processoralso configured to determine the clock value from the time stamp of thelast data stored in the memory prior to a complete power loss of therechargeable battery and to reset the clock after power is restored tothe processor by the rechargeable battery so that the next time stampincreases in time.
 2. The battery pack of claim 1, wherein the memory isan event archive.
 3. The battery pack of claim 1, wherein the datarelated to the operation of the rechargeable battery includes historydata related to the operation of the rechargeable battery.
 4. Thebattery pack of claim 1, wherein the data related to the operation ofthe rechargeable battery includes run time data.
 5. The battery pack ofclaim 1, wherein the data related to the operation of the rechargeablebattery includes data selected from the group consisting of number oftimes the battery has been charged or discharged, a maximum or minimumlifetime load test voltage, a maximum or minimum lifetime load testcurrent, a maximum or minimum lifetime load test power, a maximumlifetime peak charge temperature, a temperature sensor ID, a minimumlifetime peak charge temperature, a maximum lifetime peak dischargetemperature, a lifetime full charge cycle count, a lifetime conditioncycle count, a lifetime low power count, a lifetime wakeup count, alifetime reset count, an lifetime total fault count, a lifetime cellunder-voltage fault count, a lifetime over-current fault count and alast condition cycle time.
 6. The battery pack of claim 1, wherein thedata includes data related to identification of the rechargeablebattery.
 7. The battery pack of claim 6, wherein the data related toidentification of the rechargeable battery is a serial number.
 8. Thebattery pack of claim 1, further comprising: circuitry for determining alocation of the battery pack from location signals received by areceiver in the battery pack; and wherein the processor stores thelocation of the battery pack in the memory.
 9. The battery pack of claim8, wherein the processor stores the location of a device powered by thebattery pack in the memory.
 10. The battery pack of claim 1, wherein thesensor is an accelerometer and the processor is configured to determinedata related to forces experienced by the battery pack and alsoconfigured to store the data related to the forces experienced by thebattery pack in the memory.
 11. The battery pack of claim 1, wherein theprocessor is configured to retrieve the stored data from memory inresponse to a request for the data received from a processor external tothe battery pack.
 12. The battery pack of claim 11, wherein theprocessor external to the battery pack is programmed to request that theprocessor of the rechargeable battery communicate the data stored in thememory to a processor located in a charger, and wherein the processorlocated in the charger stores the received data in a memory associatedwith the processor located in the charger.
 13. The battery pack of claim12, wherein the processor located in the charger is configured tocommunicate the data stored in the memory associated with the processorlocated in the charger to a server remote from the charger.
 14. Thebattery pack of claim 1, wherein the processor is configured to retrievethe stored data from memory and communicate the stored data to aprocessor external to the battery pack in response to the occurrence ofan event sensed by the processor that causes the processor to execute aprogrammed command code.
 15. The battery pack of claim 14, wherein theprocessor external to the battery pack is programmed to request that theprocessor of the rechargeable battery communicate the data stored in thememory to a processor located in a charger, and wherein the processorlocated in the charger stores the received data in a memory associatedwith the processor located in the charger.
 16. The battery pack of claim15, wherein the processor located in the charger is configured tocommunicate the data stored in the memory associated with the processorlocated in the charger to a server remote from the charger.
 17. Thebattery pack of claim 1, wherein the operational parameter of the devicebeing powered by the battery pack is related to a physical parameter ofa patient upon which the device is used.
 18. A battery pack for poweringa device, comprising: a rechargeable battery having a positive and anegative terminal; a battery management system in electricalcommunication with the rechargeable battery, including a sensor formonitoring a performance parameter related to operation of therechargeable battery, a memory for storing a plurality of data relatedto operation of the rechargeable battery, or data related to anoperational parameter of a device being powered by the battery, eachdata being associated with a time stamp derived from a clock valueprovided by a clock when the data is stored in the memory; and aprocessor powered by the rechargeable battery and in electricalcommunication with the sensor and the memory, the processor configuredto receive signals from the sensor and to store the data related tooperation of the rechargeable battery extracted from the signals fromthe sensor in the memory, the processor also configured to determine theclock value from time stamp of the last data stored in the memory priorto a complete power loss of the rechargeable battery and to reset theclock after power is restored to the processor by the rechargeablebattery so that the next time stamp increases in time.